ABSTRACT: The basaltic shield volcano Erta Ale is located in the center of the Danakil desert. Erta ale is al caldera with 1.6 to 0.7 km elliptic shape and with a base of 50 km wide. The summit of Erta Ale rises from below sealevel to about 600 m altitude. One or more of Erta Ale summit craters contain lava lakes since decades.

ERTA ALE 2012

ERTA ALE 2009

The active lava lake in the south pit crater continues in 2009. The NW- pit crater has changed a lot in 2008. The local guide Meles Matwose reported that the north crater had a massive collapse in early 2008. Lava flows covering the craters flour occured at that time as well. One of the latest lava flows inside the north pit was observed by Meles Matwose in November 2008, covering parts of the new plateaus inside the crater.

Visit of Erta Ale by Chris Weber and his expedition team from 07 unil 10 Feb 2009.

The active south crater (pit) had expanded due to crater collapses to the west. The eliptic crater meassured 190 m EW and 150 m NS. There was only one platform (plateau) inside the crater about 35 meters on it's lowest point at the west side below the crater rim. The former lava lake edge from 2002 (level number 2) was still visible because of fractures and fumaroles (see figure 1. and 2. with level numbers). In 2009 area number 1. and 2. had the same level, which was a difference of 40 meters in 2002 (GVN vol. 28 April 2003). A 60 m wide active lava lake was located in the western half of the pit. Fountaining at this lava lake took place a few times per day, occasionally higher than the crater walls. Caused by this fountaining, recent lava spatter was found at the craters west edge. The level of the lava lake oscillated with babout 5 meters and came close to overlfow the plateau of level 1. and 2.

The north crater had 3 levels (number 3 to 5) in February 2009. This is quite a change in compare to 2002 were level number 3 was the only one. A massive collapse took place around one year ago. This was reported by the local guide Meles Matwose and had caused the deeper level number 4. New lava flows occured at that time as well on lever number 4. Some recent lava flows from November 2008 covered a part of a new plateau inside the crater (level number 4). Very little lava flows entered the lowest level number 5 of the NW crater. Some hornitos on level number 4 were strong degassing inside the carter and on 09 February, lava spatter (about 15 m high strombolian activity) took place at one hornito from 6 to 10 pm.

to the left: Part of Erta Ale caldera with the north and south pit (crater), based on GPS data (plot by L. Fritsch) from 2002.

to the right: The same part of Erta Ale caldera based on GPS data (plot)from February 2009. Courtesy of C. Weber.

to the left: The active lava lake in November 2002 was about meters deep inside the south pit.

to the right: The lava lake of the south pit with a much higher level, February 2009. Courtesy of C. Weber.

ERTA ALE 2002

The south crater was of ellipsoid shape of about 160m in east-west orientation and about 130m in north-south orientation. Inside the crater, about 1/2 of the area was taken up by a lava lake. The lava lake surface was about 90m below the western rim of the south pit. The reamining 1/2 area in the east were covered by basalt rock which built a terrace about 45 meters below the crater rim.
This was a little surprise to us, because the last observations found the terrace at about 70m below the rim, and widely covered with talus.
Therefore the lava lake must had risen up to the present terrace altitude between spring 2002 and our visit on December 2nd. Almost no talus was found on the terrace which indicates, that the lava cover of the terrace was not old at all. A lava sample of this new lava flows covering the terrace was taken for analyses.

Figure 1 (left): A sketch map of the active crater at Erta Ale on 2 December 2002. The elliptical crater was WE 160 m (X) and NS 130 m. The lava lake (taking part 50% of the crater) from WE was approximately 100 m. Our descents (dotted line) were made at point (D) in the north. Lava fountaining up to 20 m high occured in different areas at the crater lake, but mainly in the west, south and center. Courtesy of C. Weber

The area (A) of the three collapses are indicated with a line of stipes. At a length of about 50 m along the crater wall and with an average of 10 m wide, around 40 m of the vertical crater wall collapsed in three sequences. The second and the third collapses were a little bigger than the first one. All together we estimate a volume of 20,000 cubic meter of rocks.

Figure 2 (left): A sketch map of a cross-section of the active crater at Erta Ale on 2 December 2002 from east (E) to west (W). The altitude from the crater rim at the east (E) down to the terrace (T) was 45 m. In the north at our descent (D), indicated with the dotted line, about 40 m down to the terrace. In the west part the altitude from the crater rim (W) to the lava lake was 80 m in total (Y). Courtesy of C. Weber.

We don't know when the lava covered the former lava terrace, but we think because of the few rocks being found on the suface, that not much time has passed after this has happened. On the other hand, the fracturs in this lava layers were quite cold and therefore we estimate, that the overflows of the old terrace was about September 2002.

Several earthquakes were noticed during the stay. No seismic equipment was present, but nontheless five seismic events were well observed. On Dec. 4, 2002, a short trembling was noticed by group members in the early evening hours. The following day, on Dec. 5, at 12:40 and 13:12 local time, at both times a series of two seismic events of each 1-2 second of duration and a several-second break was noticed through ground trembling and noise. No rapid change on the lava lake was noticed at that time.
Strong fumarolic activity was inside and outsiden the NW crater. Also on the outside of the caldera rim fumaroles were found. At that places, grass is living off the water vapors, while eggshell-like gypsum structures grow in a large field around the fumarole openings.

Rockfall is not a surprise at the crater of Erta Ale, but on December 6th it was quite anusuall. In the morning hours three big rockfalls (crater wall collapses) accured with only minutes in between. About 20 000 cubic meter rocks slided down in the active lava lake. Some rocks also hitted the terrace in the east of the crater. The two image sequences abouve and following show this action. Manfred from our team took this pictures.
The avalanche hitting the lake created a large cloud of orange-brown dust which instantly filled the pit. Also, Pélées' Hair was blown out of the pit in large amounts.

In the sequence 2 (Rockfall Nr. 2), the white arrows point at the helmet of Marc and myself. Well, it looks more dramatic than it was actually. Congratulations to Manfred for these good film shots, which will certainly warn further expedions reading this.

DALLOL

The volcano Dallol has been visited more or less only by air in the last years. For sure, a flight over the Danakil is a great bird view anyway. At lake Assale, the salt mining is still going on handmade and very interesting to explore. The salt is transported by hundreds of camels to the highland marked.

Dallol can be reached by car and a tough walk through the salt desert.

ETHIOPIA

DANAKIL: After JAN 2012 incident with killed tourists at Erta Ale, a military unit has been based at Erta Ale to protect tourist groups at the volcano from the base to the top. This makes the volcano visit as safe, as it has never been. The volcano Dallol is still visited with military company.
A new road from Makale into the Danakil until the village and military base at Amadela is under construction. When this road will be finished (about 2014), then a smooth ride into the Danakil will come true.
However, to reach Erta Ale and some interesting areas of the Danakil will be still a kind of an epedition. What VEI is planing to do next will be published under "excursiones-expedition-Ethiopia" on this webside.
For the geological situation please look at VHDL.